The invention is related generally to the field of wound-fiber reinforced plastic products. More specifically, the invention is related to apparatus and methods for winding fibers and applying resin to make such wound-fiber reinforced plastic products.
Wound-fiber-reinforced plastic products are well known in the art. Some very useful wound-fiber reinforced plastic products include conduit or tubing used to carry fluids. This type of conduit is typically made by winding glass, graphite or other reinforcing fibers about a tube mandrel, a liner or other tube form. The fibers are wound in a substantially helical pattern. The fibers may be impregnated with resin prior to winding or the resin may be applied after winding. The resin is then cured in some manner to create the finished product.
Typical apparatus for making wound-fiber reinforced plastic products are described, for example in U.S. Pat. No. 3,769,127 issued to Goldsworthy et al. In general the apparatus known in the art for making wound-fiber products includes one or more winding stations which hold bobbins of the fibers to be wound on an article, and a conveyor for moving the article axially through the winding stations. The winding stations may rotate about the axis of the article, or the article may itself be axially rotated as it is moved through the winding stations. The axial motion of the article combined with relative rotation of the article through the winding stations results in the article having the reinforcing fibers wound in a generally helical pattern on the exterior surface of the article.
Some winding systems known in the art have a common drive system for axially moving the article, and rotating either the article or the winding stations. Relative fiber winding rotation rates can be changed, to apply different helical winding patterns, by selecting various gearing or drive belt pulley ratios between the axial rotator or winding station rotator and the axial article conveyor. Other winding systems include separate drivers for each winding station, such as an electric motor rotationally coupled to each winding station. The relative rotation rates of the winding stations in these systems are typically not controlled other than by controlling the speed of the motor. It is desirable to have a fiber winding system which has precisely controlled winding rates to form various wound-fiber reinforced plastic articles.
Prior art fiber winding systems include either a drip-type resin impregnator, an immersion bath, or a pressurized impregnator bath to apply resin to the fibers during manufacture of the reinforced product. These prior art resin impregnators can cause air pockets or inclusions in the finished resin. Inclusions can significantly weaken the final product. It is desirable to have a resin impregnator for fiber winding systems which minimizes the number of such inclusions.
Fiber winding systems known in the art typically do not actively control the amount of tension applied to the fibers during winding to account for the axial position of the article having fibers wound thereon or changes in fiber delivery characteristics during the winding operation. It is desirable to have a fiber winding system which can apply controlled tension to the fibers during winding thereof.
Wound-fiber reinforced tubing has become desirable for use in petroleum wellbores due to the cost and corrosive properties of steel, as is typically used for such tubing. Wound-fiber reinforced tubing made by methods and apparatus of the prior art typically do not have the tensile strength and differential pressure capacity for use in petroleum wellbores. It is desirable to have a system which can make wound-fiber reinforced tubing which has the requisite mechanical properties for use in petroleum wellbores.
Wound-fiber reinforced plastic is also desirable for use in pressure containers. Prior art methods for making wound-fiber reinforced plastic articles have not been particularly successful in producing pressure containers which have the requisite mechanical properties.
One aspect of the invention is a system for winding fibers onto an article. The system includes a winding station having a controllable speed of rotation. The winding station has at least one fiber bobbin mounted on it. A rotation sensor is rotationally coupled to the winding station. The system includes a conveyor which is adapted to move the article axially through the winding station. A speed sensor, adapted to measure an axial motion of the article through the winding station, is included in the system. The system includes a controller adapted to operate the winding station at a rotational speed corresponding to the measured axial motion of the article through the winding station, so as to apply the fibers to the article in a predetermined pattern.
In one embodiment, the rotational speed of the winding station is controlled to match the measured axial speed of the article. In one example of this embodiment, the rotational speed is controlled to maintain the lay angle of the fibers to within a tolerance of about one-half degree. In another embodiment, the rotational speed of the winding station is controlled so that the lay angle of the fibers corresponds to the axial position of the article within the winding station.
In a particular embodiment, the system includes a controllable brake rotationally coupled to the bobbin. The brake is selectively operable to maintain a substantially constant tension on the fibers as the fibers are wound onto the article. In one example, the tension on the fibers can be determined by measurement of the torque exerted by a motor used to turn the winding station. In one example, the torque can be determined by measuring the current drawn by the motor which rotates the winding station.
In another embodiment, the system includes a resin ring coupled to the winding station, wherein the fibers are impregnated with resin prior to winding onto the article. The resin ring in this embodiment includes a chamber sealed at its inlet and outlet by an inflatable seal. The resin is pumped into the chamber under pressure to impregnate the fibers.
Another aspect of the invention is a method for making a wound-fiber reinforced article. The method includes moving the article through a winding station at a measured rate of speed, rotating fibers around a circumference of the article at a measured rotational speed, and controlling the rotational speed to match the rate of speed at which the article moves through the winding station. In one embodiment of the method, the rotation rate of the winding station is selected to provide a fiber lay angle which is within a tolerance of about one half degree. In another embodiment of the method, the lay angle is selected with respect to an axial position of the article within the winding station.